The present invention relates to a receiving arrangement for a multiple type carrier, e.g. a print wheel, for use in impact printers in the form of typewriters or similar office machines.
The present invention is particularly directed to a receiving arrangement which effectively protects such a type carrier against damage mainly in the mounted operating state but also in the unmounted state, i.e. when it is removed from the machine, as is the case already with other forms of type carriers, such as, for example, band-like type carriers which are mounted on guide rollers within a cassette-like structure, carriers of this type being disclosed, for example, in German Offenlegungsschrift [Laid-open Application] No. 2,247,926.
Protective containers have already been provided for axially symmetrical, or circular, multiple type carriers to hold the type carriers in the mounted state at a rotatable setting shaft in such a way that during operation the type carriers are substantially protected against inadvertent manual contact. For example, German Offenlegungsschrift No. 2,010,206 discloses a receptacle within a machine for a disc-shaped type carrier in which the type carrier is additionally protected against soiling that may originate from gear members within the machine. As already mentioned, this receptacle is part of the machine frame which simultaneously includes the bearing means for the rotatable setting shaft of the type carrier. This has the result that an operator cannot easily remove such a type carrier from this receptacle for the purpose of exchanging it.
In the printing mechanism disclosed in German Offenlegungsschrift No. 2,455,831, which includes a disc-shaped type carrier, a protective ring is provided in the machine frame concentric with the rotatable type setting shaft so as to protect the type carrier against contact in radial directions. For the purpose of replacement, the type of carrier in this printing machanism can be removed from the rotatable setting shaft in the axial direction, the protective ring remaining in the machine, however. This has the result that, on the one hand, a type carrier that has been removed from an office machine is unprotected against damage at least until it has been deposited into a storage container and, on the other hand, the carriage may soil the operator's fingers since in its regions carrying the printing type it may be soiled considerably from the inking device of the office machine.
German Auslegeschrift [Published Application] No. 2,415,626, moreover, discloses a printing mechanism having a disc-shaped type carrier which is not brought into operating engagement with the rotatable setting shaft directly, but rather indirectly via disc-like carrier which serves to receive intermediate pieces associated with the individual printing spokes and also to receive an elastic disc which is likewise protected with spokes, these spokes cooperating, on the one hand, with the intermediate pieces and, on the other hand, being acceleratable in the axial direction of the rotatable setting shaft by a printing hammer mechanism for the indirect actuation of the associated type fingers of the type disc. The outer jacket of the disc-like carrier is provided wtih a ring which protrudes in the axial direction in such a manner that the type disc is protected against manual access. This disc-like type carrier can be fastened to the rotatable setting shaft by means of a screw element. The result is that this type carrier cannot be easily exchanged by an operator.
U.S. Pat. No. 4,127,335 discloses a receiving arrangement for a multiple type carrier, which arrangement has a structure similar to a receiving cassette. This structure has a frontal wall which acts like a shield and which, in the mounted state, faces the operator, i.e. the type carrier is exposed on the side of the shield facing the printing abutment. The type carrier is held at the shield, which is provided with laterally protruding edges of a depth at least equal to that of the thickness of the type carrier, so that the carrier is centered on the one hand, and, on the other hand, is held by friction against the frontal wall of the cassette when it is in the unmounted state. In the mounted state the type carrier is then lifted slightly away from the frontal wall in order to be able to be driven without friction by the drive shaft. A drawback of this receiving arrangement is that, in the unmounted state of the receiving arrangement, the type carrier is not positively secured against inadvertent rotation. As a result, it is necessary to conduct an extended search run of the drive shaft after each exchange of type carriers in order to provide secure engagement of the rotation following means. Moreover, this receiving arrangement cannot reliably protect the operator's fingers against soiling since the shield is completely open particularly on the side where the print type faces of the type carrier are disposed.
U.S. Pat. No. 4,124,312 also relates to a receiving arrangement for a type disc. This cassette is designed to enclose the type disc on all sides, i.e. even in the immediate printing region, which then of course creates considerable difficulties for the operator with respect to being able to see what has just been printed. The operator must practically look through a window in the cassette which is hardly possible from a normal angle of view.